1. Technical Field
The invention relates generally to an electrical nail gun, and more particularly, to a dynamic clutch apparatus that uses a flywheel to drive a firing pin set.
2. Related Art
An electrical nail gun is an electrical hand tool that uses electricity to drive a firing pin set to generate nail-percussion kinetic energy. The firing pin set must be capable of outputting tremendous liner nail-percussion kinetic energy instantaneously. Patents such as U.S. Pat. No. 5,098,004, EP1584418, EP1584419 have already disclosed electrical nail guns that use flywheels to drive firing pin sets so as to generate nail-percussion kinetic energy.
A person skilled in the relevant art knows how to make use of the characteristic that when a flywheel is driven to rotate, the flywheel can accumulate rotational kinetic energy. The person can place the firing pin set between the flywheel and a free roller (a.k.a. a pinch roller) that can move. A swinging arm mechanism can serve as a dynamic clutch apparatus, controlling the free roller to move by rotation and oscillation. The free roller than presses the firing pin set, causing the firing pin set to touch and press the flywheel. At the moment when the firing pin set touches and presses the flywheel, the flywheel passes the accumulated rotational kinetic energy to the firing pin set, causing the firing pin set to instantaneously output tremendous liner nail-percussion kinetic energy, successfully firing nail components one by one.
In addition, the U.S. Pat. No. 7,575,141 discloses an electrical nail gun unlike those disclosed by the aforementioned patents. Specifically, the U.S. Pat. No. 7,575,141 gives the free roller a fixed position, and the free roller only serves for guidance and support purposes when the firing pin set is having liner nail-percussion movement. The patent further uses a different swinging arm mechanism to serve as a dynamic clutch apparatus, controlling the rotating flywheel to move, and as a result to touch the firing pin set and to press the firing pin set to move to percuss a nail.
It deserves mentioning that the U.S. Pat. No. 7,575,141 prevents the free roller from deviating from the nail-percussion axial direction when it presses and touches the flywheel, which is a common problem of the U.S. Pat. No. 5,098,004, EP1584418, and EP1584419 patents. This problem is severe especially when a skid base of the firing pin set has worn out after multiple frictions. However, in the patents, including the U.S. Pat. No. 7,575,141, the swinging arm mechanism serves as a dynamic clutch apparatus. When the firing pin set is being pressed by the free roller and the flywheel on two sides to pass kinetic energy, the swinging arm and the gun body support inevitably suffer from tremendous bending moment applied by the free roller or the flywheel. The bending moment is a bending load of the swinging arm; the swinging arm mechanism and the gun body support must be thick and strong enough to cope with the bending load. As a result, the swinging arm mechanism and the gun body support occupy too much volume of the gun body and add too much additional weight.